Organic Light-Emitting Diode (OLED) display device is widely recognized as the next generation display technology due to its advantage of high brightness, fast response, low energy consumption and flexibility. Wherein, compared with a liquid crystal display (LCD), the biggest advantage of an OLED display device is that it can be made into ultra-thin, transparent, flexible, foldable display devices. A method for making a flexible OLED display device is generally to form a flexible substrate on a glass substrate. After preparing a thin film transistor layer and a pixel array layer on the flexible substrate, the flexible substrate and the glass substrate are separated to obtain a flexible OLED display device.
The inventors of the present application have found during their long time research that alignment marks are usually provided on a flexible substrate to facilitate alignment between the mask plate and the glass substrate when the pixel array layer is prepared by a vapor deposition method and using a mask plate. However, since the color of the flexible substrate is dark yellow and the deposition process is carried out with a face-down coating method, the alignment marks cannot be caught at the preparation of the pixel array layer, resulting in failure of alignment. In addition, due to the high temperature in the vapor deposition process, the flexible substrate is prone to deformation, resulting in the alignment not accurate and color mixed in vapor deposition.